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(11) | EP 0 272 721 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Bobbin support arm with modulation of motion transmission between the roller and bobbin |
| (57) A bobbin support arm with modulation of the motion transmission between the roller
and bobbin to prevent ribbing, by means of a rocker movement between the bobbin and
roller determined by the oscillation of the arm both in the horizontal plane and in
the vertical plane. |
[0001] This invention relates to a device for modulating the motion transmitted by the bobbin drive roller in a bobbin winding station. The invention is described with reference to a winding machine, but can also find advantageous application in other operations in the textile industry, such as twisting and the like. It relates to bobbin winding both in machines in which the yarn is guided by slots or grooves provided along a spiral path in the bobbin drive roller, and in machines with a separate yarn guide.
[0002] The bobbin is commonly driven by a rotary drum - in a form of a right cylinder or cone of small taper - which is kept in contact therewith along a generating line common to the two members. The technical problem to which the present invention relates derives from the fact that during spooling, the rotary drum remains of constant shape and size, whereas the bobbin which gradually grows because of the yarn wound on it changes continuously in terms of its size and/or shape.
[0003] If motion takes place under perfect friction, the peripheral speed of the drive drum coincides substantially with the linear winding speed of the yarn.
[0004] In a very common type of winding machine, the drive drum, usually known as the roller, carries in that surface which engages the bobbin a spiral groove in which the yarn is engaged and guided so as to wind on the bobbin in a spiral pattern. In another type of winding machine, now obsolete because of its poor productivity, the yarn is distributed over the bobbin surface by a yarn guide made to travel with periodic motion along the bobbin generating line.
[0005] As the bobbin size increases, its linear yarn winding speed remains substantially constant - and this is a necessary condition for proper execution of this operation - but its angular speed decreases linearly.
[0006] As the yarn travels along the contact generating line in a constant time, the number of turns wound for each travel stroke of the yarn guide decreases slightly but continuously with each successive layer.
[0007] The number of turns used for forming the complete spiral layer therefore decreases, as the turns become longer.
[0008] The phenomenon therefore occurs in which when the spiral generated by the to-and-fro travel of the yarn contains an exact whole number of turns, the next spiral commences exactly superimposed on the preceding.
[0009] An analogous drawback - although increasingly less serious - takes place when, instead of a whole number, the generated spiral contains a number of turns n¹/2, n¹/3, n¹/4 ...., where n is a positive whole number, and corresponds to the phenomenon of generating 2, 3, 4 ... layers of spirals which each commence superimposed on the preceding.
[0010] This phenomenon is commonly known as ribbing, and means that the bobbin becomes either unusable or of poor quality.
[0011] Ribbed bobbins are difficult to unwind in the subsequent operations, are of variable compactness between their parts so that they cannot be correctly dyed and there is the risk of having to then discard them, and in addition the quantity of wound yarn no longer corresponds to the bobbin size.
[0012] To prevent rib formation it is therefore necessary to avoid an exact ratio - at least for a short time - between the bobbin being wound and the yarn guide device.
[0013] The known art uses various expedients for this purpose. The most common expedients are based on discontinuity of roller operation. This can be obtained by periodically raising the bobbin out of contact with the roller. The bobbin continues to rotate while slowing down, until contact with the roller is restored. Alternatively, the roller operation can be interrupted periodically by switching off the supply to its electric drive motor or by disconnecting the roller from the motor.
[0015] This type of expedient, although widely used, has considerable drawbacks because its effect varies as the size of the bobbin being formed varies.
[0016] Its application to right cylindrical bobbins is also problematic because on restoring operation, consistency of the contact speed must be re-established along the entire generating line.
[0017] A different expedient uses axial reciprocal movement between the roller and bobbin, produced by periodically displacing their shafts, for example by the action of a cam.
[0019] This expedient enables the ribs to be flattened but not eliminated, because excessive travel would deform the bobbin in an unacceptable manner.
[0020] A further expedient was based - in the case of the obsolete yarn-guide winding machines - on varying their drive transmission ration, so varying the travel time (varying the travel time would be equivalent to the previously described expedient).
[0021] With the obsolescence of yarn-guide winding machines, this expedient is no longer implemented, but even in yarn-guide winding machines these reciprocating motion members presented considerable problems in varying their speed.
[0022] A further expedient uses periodic rocking action along the generating line between the roller and the bobbin by varying their effective contact diameter. By this means, a variation in the bobbin speed is obtained, enabling the spiral commencement points to be offset.
[0023] This expedient offers substantially no drawback when forming conical bobbins, whereas drawbacks are encountered when this action is used in the production of right cylindrical bobbins. Varying the effective contact diameter is somewhat difficult, because the mass of yarn already wound and accumulated on the bobbin has to be significantly deformed.
[0025] In contrast, the present invention enables the transmission ratio between the roller and bobbin to be regulated by varying the relative position of these latter in a rocking manner not fixedby the generating line, while keeping them always in contact, and thus without requiring substantial deformation even in the case of right cylindrical bobbins.
[0026] For a correct understanding of the interactions between a conical bobbin and a right cylindrical roller which rotate in contact along a generating line, it must be remembered that within the contact segment there exists only one point on the conical bobbin, known as the neutral point, which is driven at the same peripheral speed as that at which the roller rotates. The peripheral speed increases from that point in the direction of the major base and consequently the bobbin slides on the roller and proceeds faster than it, whereas from that point in the direction of the minor base the bobbin slides on the roller and proceeds slower than it.
[0027] The aforesaid rocking action in effect moves this neutral point along the contact segment. As the bobbin is deformable, this translation of the contact point takes place gradually along the line of contact.
[0028] The device according to the present invention consists of a bobbin support arm and is described hereinafter in terms of a typical embodiment shown on the accompanying figures.
[0029] Figure 1 is a perspective overall view, Figure 2 is a view on the horizontal plane xy, and Figure 2A is a side view on the plane yz.
[0030] The driver roller 1, provided with yarn guide grooves, not shown, rotates clockwise to consistently drive the bobbin 2, which rotates in the opposite direction.
[0031] The bobbin 2 is supported on a pair of centres 3 and 4 supported by the asymmetric fork 5, which is of a size sufficient to house the finished bobbin. The fork 5 comprises in its end 6 a cylindrical cavity in which a long pin 7 is disposed, and is fixed at 5 by a dowel 8 - or an equivalent means - which enables the inclination of the axis of the centres 3 and 4 to the axis of the roller 1 to be adjusted as required, in order to be able to use tubes of different taper.
[0032] On the extension of the end 6, and adjacent thereto, there is located a member 9 provided with a precision through bore for the pin 7, which extends beyond that face thereof distant from the end 6. The member 9 is connected by an articulated quadrilateral, formed from two non-parallel connecting rods 10 and 11 which enable the member 9 to move with rotary motion about the centre C defined by the point at which the axes of the connecting rods 10 and 11 intersect, to the support 12 which can rotate only in a vertical plane about the pivot 13.
[0033] The rotation of the support 12 is determined by the increase in the diameter of the bobbin or by external action to raise the fork 5. Rotating the support 12 results in the inclination of the rotation plane of the support 9.
[0034] Rigid with the member 12 there is a device 14 for driving the member 9 with reciprocating motion, and indicated by way of example as a rotating cam, but which can be in the form of a connecting rod and crank or other linkages known to the art, to cause the member 9 to oscillate about the centre C and induce an oscillatory movement in the bobbin 2 by way of the pin 7, the fork 5 and the centres 3 and 4.
[0035] The pin 7 terminates in a transverse bar 15 connected to a fixed part by two ball joints 16 and 17 which are connected together by an intermediate bar 18. The centre of rotation of the second joint 17 lies preferably on the axis of the pivot 13 or in proximity to it.
[0036] With reference to Figure 3A, the operation of the device 14 causes the member 9 to oscillate, and this oscillation influences the contact of the bobbin 2 - which for ease of representation is shown in its initial stage - with the roller 1.
[0037] The bobbin 2 moves continuously from the position shown by full lines, which corresponds to the member 9 in its position of maximum withdrawal, to the position shown by dashed lines, which corresponds to the member 9 in its opposite position of maximum advancement.
[0038] As a result of the oscillation of the member 9, which causes consistent oscillation of the axis of the pin 7, the restraint formed by the ball joints 16 and 17 causes the pin 7 to rotate about its axis. This rotation generates in the fork 5 and bobbin 2 the rocking movement in the vertical plane shown in Figure 3B. The movements of Figures 3A and 3B combine to generate a neutral point trajectory which non longer coincides with the generating line.
[0039] With regard to the behaviour of cylindrical bobbins, it should be noted that the motion shown in Figure 3A consists both of axial translation and of rotation of the bobbin axis about the roller axis, these consequently no longer lying in the same plane. As a consequence of said rotation, the speed - both peripheral and angular - of the bobbin 2 is reduced by the cosine of α, where α is the angular value of the rotation.
1. A bobbin support arm for roller-driven bobbin winding stations, able to modulate
the motion transmission between the drive roller and the driven bobbin in order to
prevent rib formation, consisting of a fork 5 for supporting the centres which support
the tube of the bobbin under formation and which rests on the drive roller, said fork
being capable of rotary movement about a pin 7 with its axis substantially orthogonal
to the axis of the centres - ie of the bobbin - said pin being connected at its opposite
end to a fixed part by means of a double ball joint 16 and 17; an articulated quadrilateral
9, 10, 11, 12 hinged within its element 12 so as to rotate substantially in the vertical
plane and secured within the opposite element 9 to the pin 7 by a through bore which
enables it only to rotate freely about its axis, said two elements being connected
together by non-parallel connecting rods 10 and 11 which move to determine rotary
oscillation of the element 9 substantially about the centre C defined as the point
at which the axes of the connecting rods 10 and 11 intersect; and reciprocating-motion
operating means 14 which generate a to-and-fro movement in the element 9 substantially
in the direction of the axis of the pin 7 and about the centre C to generate combined
rocking movements of the type shown in Figures 3A and 3B in the bobbin being wound.
2. A bobbin support arm as claimed in claim 1, characterised in that the centre of
the ball join 17 lies on the axis of rotation of the element 12 or in proximity to
it.
3. A bobbin support arm as claimed in one or more of the preceding claims, characterised
in that the reciprocating motion operating means 14 consist of a rotating cam or a
connecting rod and crank.
4. A bobbin support arm as claimed in one or more of the preceding claims, characterised
in that the angular relationship between the position of the pin 7 and the position
of the fork 5 is regulated as a function of the taper of the bobbin to be formed.